减少沥青路面横向裂缝的措施

随着交通量不断增长,车辆重载、超载现象日益严重。沥青路面通车一段时间后,常常出现不同程度的横向裂缝。分析了沥青路面横向裂缝产生的原因和危害,同时提出了相应的裂缝防治措施。     

OPTIMAL MAINTENANCE SCHEDULING FOR WATER DISTRIBUTION SYSTEMS

The scheduling of maintenance for water distribution systems is a complex task encompassing a wide range of alternatives. The methodology presented in this paper can consider the major piping alternatives of replacing and cleaning, and relining. It also considers the potential of pumping improvements while accounting for the costs of maintenance, failure and operations for a multiple-period planning horizon. To solve the problem a nonlinear optimization model is linked with a network simulation model. The application showed that the procedure can determine solutions in reasonable times.     

Effect of dietary and synthetic chelating agents on the intestinal absorption of lead

The effect of a number of dietary and synthetic chelating agents on the intestinal absorption of lead has been examined using the everted sac preparation and the tracer isotope ²⁰³Pb. All the agents examined increased lead transport into the serosal compartment. An explanation of the way in which these agents modify the model to describe lead transport is proposed.     

Predicting Chicago's Land Use Pattern

The planning of community facilities requires accurate quantitative estimates of the area, type, intensity, and location of land uses required by the growth of urban activities. The distribution of these activities and the intensity of their use of land are highly related to accessibility as measured by distance from the CBD. This paper outlines a procedure whereby area-wide estimates of future population and economic activity can be distributed to small subareas so that measures of local land requirements may be obtained.     

Data Processing for City Planning

In city planning, data-processing machines permit the rapid handling and summarization of data in housing, renewal, land use, transportation, and basic urban research. Electronic computers. specifically, are exciting because they offer a means of solving complex city planning problems, especially in forecasting land use and travel demand.

For most planning operations punched card data processing is superior to other processes. The functions of these machines are described herein and three examples of data processing are elaborated on. In future years, planning techniques may have to be altered considerably to take advantage of the potentials of data processing.     

广西建筑科学研究设计院住宅楼基坑支护方案比较

广西建筑科学研究院高层住宅工程基坑深约9.3m,为确保安全经济、技术可靠,采用内支撑排桩支护结构和扩大头锚杆支护结构两个方案进行技术、造价等方面的对比,并考虑施工过程的影响,结果表明扩大头锚杆支护在技术经济方面占优,被确定为实施方案。     

GO纳米片层对水泥水化晶体及胶砂力学性能的影响

通过控制氧化反应时间和超声波处理,制备了含氧量(质量分数,下同)分别为19.15％,25.43％和32.30％的氧化石墨烯(GO)纳米片层分散液,研究了不同含氧量GO纳米片层对水泥水化晶体和胶砂力学性能的影响.结果表明:含氧量为25.43％的GO纳米片层能够促使水泥水化反应形成规整的花状晶体,同时使得胶砂的拉伸强度和抗折强度显著提高.阐述了GO纳米片层调控水泥水化晶体的作用机理,认为GO纳米片层对水泥水化晶体的形成具有模板作用.     

Polychlorinated naphthalenes in air and snow in the Norwegian Arctic: a local source or an Eastern Arctic phenomenon?

PCNs were measured in air and snow during separate field campaigns at Ny-Alesund (April 2001) and Troms? (February/March 2003) in the Norwegian Arctic. Air concentrations ranged from 27 to 48 and 9 to 47 pg sigmaPCN m(-3) for Ny-Alesund (n=6) and Troms? (n=10), respectively. These concentrations (including the tri-chlorinated naphthalenes) greatly exceeded concentrations previously measured in the Canadian Arctic, but did fall within the upper range of concentrations observed over the eastern Arctic Ocean and regional seas. Local sources appear to be affecting concentrations observed at both sites, with the presence of several hexa-chlorinated naphthalenes at Troms? probably attributed to local/regional sources. Use of air mass back trajectories at Troms? revealed that background air concentrations in the Norwegian Arctic are likely to range between <9 and 20 pg sigmaPCN m(-3) and that contemporary concentrations derived close to potential sources (i.e. arctic towns) may equal or exceed those of PCBs. The mean concentration in surface snow was 350 and 240 pg sigmaPCN L(-1) (meltwater) (or 0.014 and 0.01 pg g(-1) (snow)) at Ny-Alesund and Troms?, respectively. The wide variation in concentrations observed between fresh snowfalls could be explained by different snow densities (as a surrogate of snow surface area), rather than attributed to varying air concentrations. A statistically significant inverse relationship was found between snow density and concentrations of tri- to penta-chlorinated homologues and compliments similar findings for the polychlorinated biphenyls (PCBs). This suggests that the vapour-sorbed quantity changes rapidly with snow ageing/compaction; with implications for the fate of these chemicals in the Arctic.